350 Shark and Company 



heads— each about 30 inches long— are found in nets along the outer 

 shore of Long Island in August. Hammerheads are also in New York 

 waters from July to October. They disappear suddenly when the water 

 temperature falls below 67 °F. Where they go after that is not known. 

 Common Hammerheads, which occasionally grow to 13 feet in length, 

 also roam the eastern Atlantic, from Portugal and occasionally the British 

 Isles to South Africa. They are also found in the Gulf of Mexico, along 

 both sides of the Pacific, and in the Indian Ocean. 



Why do Hammerheads have hammerheads? One unproved theory 

 is that they use their variously styled flat heads as steering planes, similar 

 to the diving planes of the hulls of submarines. By moving their heads 

 agilely they can quickly turn, dive, and ascend. The Hammerhead's 

 head is also, in effect, a big flat nose, since grooves for scent detection 

 run along its entire leading edge. 



Family Squalidae—SpiNY Dogfishes 

 The many species in this family have two features in common. Pro- 

 jecting before each dorsal fin is a quill-like spine. Further, none of these 

 sharks has an anal fin. The most common species— indeed, one of the 

 most abundant of all sharks— is the Spiny dogfish {Squalus acanthias 

 Linnaeus, 1758), also known as the Piked dogfish. Skittle-dog, Thorndog, 

 Codshark, and Spur dog. 



Like a seething carpet flung by some nemesis of fishermen, gigantic 

 schools of Spiny dogfish descend upon fishing grounds, where they 

 devour or mutilate netted fish, eat both bait and captives on hand-lines, 

 tear nets to shreds, and raid lobster pots. In some fishing grounds, Spiny 

 dogfish bring fishing to a stop until, their ravenous hunger satisfied 

 or all the fish that survive have fled, they move on in search of more 

 prey. 



Damage to gear and loss of fish cost our fishermen millions of dol- 

 lars a year, since fishermen in the United States and Canada cannot sell 

 the Spiny dogfish except for fertilizer and such oil as may be had from 



A Spiny dogfish (Squalus acanthias). 



Courtesy, Harvard Museum of Comparative Zoology 



